U.S. patent number 8,591,020 [Application Number 13/379,132] was granted by the patent office on 2013-11-26 for aqueous ink jet ink comprising a crosslinking pigment dispersion based on diblock polymeric dispersants.
This patent grant is currently assigned to E I du Pont de Nemours and Company. The grantee listed for this patent is Xiaoqing Li, Patrick F. McIntyre, C. Chad Roberts. Invention is credited to Xiaoqing Li, Patrick F. McIntyre, C. Chad Roberts.
United States Patent |
8,591,020 |
Li , et al. |
November 26, 2013 |
Aqueous ink jet ink comprising a crosslinking pigment dispersion
based on diblock polymeric dispersants
Abstract
The present disclosure provides an aqueous ink jet ink
comprising an ink vehicle and an aqueous dispersion, wherein the
aqueous dispersion comprises a solid particle and a polymeric
dispersant that has been crosslinked, wherein the polymeric
dispersant is a block copolymer comprising an A block and a B
block, wherein the A block is a segment having a block size of
about 5 to about 18 units, and comprises at least 50% by weight of
a monomer, having the following structure:
CH.sub.2.dbd.CRC(O)O(CHR.sub.1CH.sub.2O)nR.sub.2; wherein R and
R.sub.1 are H, or methyl; R.sub.2 is alkyl of 1-4 carbon atoms or
phenyl; and n is about 1 about 20; and the B block is a segment
comprising an ionic monomer and at least one hydrophobic monomer;
and wherein the dispersant comprises a crosslinkable moiety;
wherein the crosslinkable moiety is crosslinked with a crosslinking
agent selected from the group consisting of epoxide, carbodiimide,
oxazoline, isocyanate, and silane; and wherein the aqueous
dispersion has a pH of at least about 8.0. The disclosure further
pertains to a printer comprising the aqueous ink jet ink of this
disclosure that provides images with the requisite optical density
and chroma needed for emerging ink jet applications.
Inventors: |
Li; Xiaoqing (Newark, DE),
Roberts; C. Chad (Hockessin, DE), McIntyre; Patrick F.
(West Chester, PA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Li; Xiaoqing
Roberts; C. Chad
McIntyre; Patrick F. |
Newark
Hockessin
West Chester |
DE
DE
PA |
US
US
US |
|
|
Assignee: |
E I du Pont de Nemours and
Company (Wilmington, DE)
|
Family
ID: |
42537786 |
Appl.
No.: |
13/379,132 |
Filed: |
July 14, 2010 |
PCT
Filed: |
July 14, 2010 |
PCT No.: |
PCT/US2010/041912 |
371(c)(1),(2),(4) Date: |
December 19, 2011 |
PCT
Pub. No.: |
WO2011/008813 |
PCT
Pub. Date: |
January 20, 2011 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20120105558 A1 |
May 3, 2012 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
61225741 |
Jul 15, 2009 |
|
|
|
|
Current U.S.
Class: |
347/100 |
Current CPC
Class: |
C09D
11/326 (20130101) |
Current International
Class: |
C09D
11/00 (20060101) |
Field of
Search: |
;347/100 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0 851 010 |
|
Jul 1998 |
|
EP |
|
1 167 470 |
|
Jan 2002 |
|
EP |
|
2006-312724 |
|
Nov 2006 |
|
JP |
|
WO 00/20520 |
|
Apr 2000 |
|
WO |
|
WO 2004/104119 |
|
Dec 2004 |
|
WO |
|
WO 2006/064193 |
|
Jun 2006 |
|
WO |
|
WO 2006/107112 |
|
Oct 2006 |
|
WO |
|
WO 2006/138311 |
|
Dec 2006 |
|
WO |
|
Other References
ISR and WO of the ISA in PCT/US2010/041912, PCT counterpart of the
present application, European Patent Office, Rijswijk, NL, Damiano
Vizzini, Authorized Officer [ISR] and Volker Schmitz, Authorized
Officer [WO of the ISA], Aug. 26, 2010. cited by applicant .
Wojciech Zeslawski, Authorized Officer, Written Opinion of the
International Searching Authority, in WO 2010/059939,
PCT/US2009/065330, PCT counterpart of copending U.S. Appl. No.
13/125,599, European Patent Office, Munich DE, May 20, 2011. cited
by applicant .
Damiano Vizzini, Authorized Officer, International Search Report
and Written Opinion, in WO 2011/008810, PCT/US2010/041904, PCT
counterpart of copending U.S. Appl. No. 13/379,121, European Patent
Office, Riswijk NL, Nov. 5, 2010. cited by applicant .
Damiano Vizzini, Authorized Officer, International Search Report
and Written Opinion, in WO 2011/008820, PCT/US2010/041921, PCT
counterpart of copending U.S. Appl. No. 13/379,141, European Patent
Office, Riswijk NL, Aug. 31, 2010. cited by applicant.
|
Primary Examiner: Martin; Laura
Attorney, Agent or Firm: Lamming; John H. Xu; Simon L.
Claims
What is claimed is:
1. An aqueous ink jet ink comprising an ink vehicle and an aqueous
dispersion, wherein the aqueous dispersion comprises a solid
particle and a polymeric dispersant that has been crosslinked,
wherein the polymeric dispersant is a block copolymer comprising an
A block and a B block, wherein the A block is a segment having a
block size of about 5 to about 18 units, and comprises at least 50%
by weight of a monomer, having the following structure:
CH.sub.2.dbd.CRC(O)O(CHR.sub.1CH.sub.2O)nR.sub.2 wherein R and
R.sub.1 are H, or methyl; R.sub.2 is alkyl of 1-4 carbon atoms or
phenyl; and n is about 1 about 20; and the B block is a segment
comprising an ionic monomer and at least one hydrophobic monomer;
and wherein the dispersant comprises a crosslinkable moiety;
wherein the crosslinkable moiety is crosslinked with a crosslinking
agent selected from the group consisting of epoxide, carbodiimide,
oxazoline, isocyanate, and silane; and wherein the aqueous
dispersion has a pH of at least about 8.0.
2. The aqueous ink jet ink of claim 1 wherein the solid particle is
selected from the group consisting of a colorant, filler, metallic
particle, biologically active compound, pharmaceutically active
compound, polymer particle and hollow glass sphere.
3. The aqueous ink jet ink of claim 1 wherein the A block has a
block size of about 6 to about 12 units.
4. The aqueous ink jet ink of claim 1 wherein the A block has about
60 to about 100% of the monomer having the specified formula.
5. The aqueous ink jet ink of claim 4 wherein the A block has about
80 to about 95% of the monomer having the specified formula.
6. The aqueous ink jet ink of claim 1 wherein the B block has a
block size of about 15 to about 80 units.
7. The aqueous ink jet ink of claim 1 wherein the polymeric
dispersant has a number average Molecular Weight (Mn) in the range
of between about 2,000 to about 20,000 Daltons.
8. The aqueous ink jet ink of claim 1 wherein n is about 1 to about
10.
9. The aqueous ink jet ink of claim 1 wherein the polymeric
dispersant has an acid number of about 40 to about 220 (mg KOH/g
polymer solids).
10. The aqueous ink jet ink of claim 1 wherein the A block monomer
is selected from the group consisting of ethoxy triethylene glycol
methacrylate, n-butoxyethyl methacrylate, and mixtures thereof.
11. The aqueous ink jet ink of claim 1 wherein the A block further
comprises monomers selected from the group consisting of
hydroxyethylmethacrylate, methyl methacrylate, methacrylic acid,
butyl methacrylate, and 2-dimethylaminoethyl methacrylate.
12. The aqueous ink jet ink of claim 1 wherein the B block
comprises a hydrophobic monomer having the formula:
R.sub.3R.sub.4C.dbd.R.sub.5X wherein R.sub.3-R.sub.5 are
independently selected from the group consisting of H, alkyl, aryl
and alkylaryl of 1 to 20 carbon atoms, and X is a hydrophobic
group.
13. The aqueous ink jet ink of claim 12 wherein X is selected from
the group consisting of: (a) an alkyl, aryl and alkylaryl group
containing 1-20 carbon atoms; (b) a group of the formula
C(O)OR.sub.6, wherein R.sub.6 is selected from the group consisting
of an alkyl, aryl and alkylaryl group containing 1-20 carbon atoms;
and (c) a group of the formula C(O)NR.sub.7R.sub.8, wherein each of
R.sub.7 and R.sub.8 is independently selected from the group
consisting of H and an alkyl, aryl and alkylaryl group containing
1-20 carbon atoms.
14. The aqueous ink jet ink of claim 13 wherein (a), (b) or (c)
further comprises one or more heteroatoms.
15. The aqueous ink jet ink of claim 12 wherein the hydrophobic
monomer is selected from the group consisting of benzyl
methacrylate, butyl methacrylate, methyl methacrylate, ethyl
methacrylate, propyl methacrylate, hexyl methacrylate, 2-ethylhexyl
methacrylate, octyl methacrylate, lauryl ethacrylate, stearyl
methacrylate, phenyl methacrylate, phenoxyethyl methacrylate,
methacrylonitrile, glycidyl methacrylate, p-tolyl methacrylate,
sorbyl methacrylate, methyl acrylate, ethyl acrylate, propyl
acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate,
octyl acrylate, lauryl acrylate, stearyl acrylate, phenyl acrylate,
phenoxyethyl acrylate, acrylonitrile, glycidyl acrylate, p-tolyl
acrylate, sorbyl acrylate, styrene, alpha-methyl styrene,
substituted styrenes, N-alkyl acrylamides, N-alkyl methacrylamides,
vinyl acetate, vinyl butyrate and vinyl benzoate.
16. The aqueous ink jet ink of claim 1 wherein the ionic monomer
has the formula: R.sub.9R.sub.10C.dbd.R.sub.11Z wherein each of
R.sub.9 - R.sub.11 are independently selected from the group
consisting of H and an alkyl, aryl or alkylaryl group having 1-20
carbons, and wherein Z is at least one ionic or a potentially ionic
monomer.
17. The aqueous ink jet ink of claim 16 wherein Z is anionic,
cationic, amphoteric or zwitterionic.
18. The ink jet ink of claim 17 wherein Z comprises an anionic
group selected from the group consisting of sulfonates, sulfate,
sulfosuccinate, carboxylate, and phosphate.
19. The aqueous ink jet ink of claim 1 wherein the crosslinkable
moiety is selected from the group consisting of acid, hydroxyl and
mixtures thereof.
20. A printer comprising an aqueous ink jet ink wherein the aqueous
ink jet ink comprises an ink vehicle and an aqueous dispersion,
wherein the aqueous dispersion comprises a solid particle and a
polymeric dispersant that has been crosslinked, wherein the
polymeric dispersant is a block copolymer comprising an A block and
a B block, wherein the A block is a segment having a block size of
about 5 to about 18 units, and comprises at least 50% by weight of
a monomer, having the following structure:
CH.sub.2.dbd.CRC(O)O(CHR.sub.1 CH.sub.2O)n R.sub.2 wherein R and
R.sub.1 are H, or methyl; R.sub.2 is alkyl of 1-4 carbon atoms or
phenyl; and n is about 1 about 20; and the B block is a segment
comprising an ionic monomer and at least one hydrophobic monomer;
and wherein the dispersant comprises a crosslinkable moiety;
wherein the crosslinkable moiety is crosslinked with a crosslinking
agent selected from the group consisting of epoxide, carbodiimide,
oxazoline, isocyanate, and silane; and wherein the aqueous
dispersion has a pH of at least about 8.0.
Description
BACKGROUND OF THE DISCLOSURE
This disclosure relates to novel, stable aqueous dispersions of
solid particles, the crosslinked polymeric dispersants that produce
the stable aqueous particle dispersions, the process of making the
same and the use thereof in ink jet inks. These dispersants enable
a unique combination of ionic and steric stabilization. In water,
they provide only ionic stabilization with a random ionic block,
but with the addition of ink vehicle components, these dispersants
facilitate entropic repulsion and steric stabilization with an ink
vehicle soluble block. Furthermore, these dispersants comprising
crosslinkable moieties are crosslinked with a crosslinking compound
such that the particles are dispersed in a crosslinked polymer
matrix.
Aqueous dispersions of solid particles are known in the art and
have been used in various applications such as, for example, inks
for printing (particularly ink jet printing); waterborne paints and
other coating formulations for vehicles, buildings, road markings
and the like; cosmetics; pharmaceutical preparations; etc. For
examples, pigment particles are typically not soluble in an aqueous
ink vehicle; it is often required to use dispersing agents, such as
polymeric dispersants or surfactants, to produce a stable
dispersion of the pigment in the ink vehicle.
An application of the present disclosure relates to an ink
(printing liquid) useful for writing utensils such as aqueous ball
point pens, fountain pens and felt-tip pens; continuous and
on-demand type inkjet printers of a thermal jet type, a piezo type
and the like; and an inkjet printing method employing the ink.
Aqueous particle dispersions generally are stabilized by either a
non-ionic or ionic technique. When the non-ionic technique is used,
a polymer having a non-ionic hydrophilic section that extends into
the water medium is typically employed. The hydrophilic section
provides entropic or steric stabilization that stabilizes the solid
particles in the aqueous ink vehicle. Polyvinyl alcohol,
cellulosics, ethylene oxide modified phenols and ethylene
oxide/propylene oxide polymers may be used for this purpose.
While the non-ionic technique is not sensitive to pH changes or
ionic contamination, it has a major disadvantage in that the
printed image is water sensitive. Thus, non-ionic content should be
minimized to ensure durability.
In the ionic technique, the solid particles are stabilized using
the polymer of an ion containing monomer, such as neutralized
acrylic, maleic or vinyl sulfonic acid. The polymer provides
stabilization through a charged double layer mechanism whereby
ionic repulsion hinders the particles from flocculation. Since the
neutralizing component tends to evaporate after printing, the
polymer then has reduced water solubility and the printed image is
not water sensitive.
There has been effort in the art directed at improving the
stability of the dispersions so that the particles are less likely
to settle out of the vehicle under defined set of conditions. The
effort to improve dispersion stability to date has included
improvements in the processes used to make the dispersions, the
development of new dispersants and the exploration of the
interaction between dispersants and particle, and between
dispersants and aqueous vehicle. While much of the effort has
general application at improving dispersion stability, some of that
effort has not found utility in particular applications. For
example, the pigment dispersions used in ink jet printing
applications have very unique and demanding requirements. It is
critical that ink components comprising the pigment dispersion
remain stable, not only in storage but also over repeated jetting
cycles.
There continues to be a need for highly stable, higher-quality and
different property inks for inkjet ink applications. Although
improvements in polymeric dispersants have significantly
contributed to improved inkjet inks, the current dispersants still
do not provide inks with requisite stability, optical density and
chroma needed for emerging ink jet applications.
SUMMARY OF THE DISCLOSURE
In a first aspect, the disclosure provides an aqueous ink jet ink
comprising an ink vehicle and an aqueous dispersion, wherein the
aqueous dispersion comprises a solid particle and a polymeric
dispersant that has been crosslinked, wherein the polymeric
dispersant is a block copolymer comprising an A block and a B
block, wherein the A block is a segment having a block size of
about 5 to about 18 units, and comprises at least 50% by weight of
a monomer, having the following structure:
CH.sub.2.dbd.CRC(O)O(CHR.sub.1CH.sub.2O)nR.sub.2 wherein R and
R.sub.1 are H, or methyl; R.sub.2 is alkyl of 1-4 carbon atoms or
phenyl; and n is about 1 about 20; and the B block is a segment
comprising an ionic monomer and at least one hydrophobic monomer;
and wherein the dispersant comprises a crosslinkable moiety;
wherein the crosslinkable moiety is crosslinked with a crosslinking
agent selected from the group consisting of epoxide, carbodiimide,
oxazoline, isocyanate, and silane; and wherein the aqueous
dispersion has a pH of at least about 8.0, more typically about 8.0
to about 12.0, and most typically about 8.0 to about 11.0.
Typically the solid particle is selected from the group consisting
of a colorant such as pigment or insoluble dye, fillers such as
silica, metallic particles, biologically active compounds,
pharmaceutically active compounds, polymer particles and hollow
glass spheres.
DETAILED DESCRIPTION OF THE DISCLOSURE
The aqueous dispersions of this disclosure comprise a solid
particle and a crosslinked polymeric dispersant. Further the ink
jet inks comprise an ink vehicle and the aqueous dispersions. These
inks provide images with the requisite stability, optical density
and chroma needed for emerging ink jet applications.
Aqueous Dispersions:
Solid Particle:
Although solid particles are required for the disclosure, the type
and composition of the solid particle is not particularly critical
and will largely depend upon the ultimate end use application of
the aqueous dispersion. By definition, the solid particle is at
least substantially insoluble in the liquid vehicle, typically
water. Apart from that general limitation, the solid particle may
be organic, inorganic or mixtures thereof. Some examples of
suitable solid particles include colorants such as pigments and
insoluble dyes, fillers such as silica, metallic particles,
biologically active compounds, pharmaceutically active compounds,
polymer particles, hollow glass spheres, etc.
A wide variety of organic and inorganic pigments, alone or in
combination, may be selected to make the aqueous dispersion and ink
jet ink. The term "pigment" as used herein means an insoluble
colorant. The pigment particles are sufficiently small to permit
free flow of the ink through the ink jet printing device,
especially at the ejecting nozzles that usually have a diameter
ranging from about 10 micron to about 50 micron. The particle size
also has an influence on the aqueous dispersion stability, which is
critical throughout the life of the ink jet ink. Brownian motion of
minute particles will help prevent the particles from flocculation.
It is also desirable to use small particles for maximum color
strength and gloss. The range of useful particle sizes is typically
about 0.005 micron to about 15 micron. Typically, the pigment
particle size is in the range from about 0.005 to about 5 micron
and, most typically, from about 0.005 to about 1 micron. The
average particle size as measured by dynamic light scattering is
less than about 500 nm, typically less than about 300 nm.
The selected pigment(s) may be used in dry or wet form. For
example, pigments are usually manufactured in aqueous media and the
resulting pigment is obtained as water-wet presscake. In presscake
form, the pigment is not agglomerated to the extent that it is in
dry form. Thus, pigments in water-wet presscake form do not require
as much deflocculation in the process of preparing the inks as
pigments in dry form. Representative commercial dry pigments are
listed in U.S. Pat. No. 5,085,698, incorporated herein by
reference.
Some examples of pigments with coloristic properties useful in ink
jet inks include: (cyan) Pigment Blue 15:3 and Pigment Blue 15:4;
(magenta) Pigment Red 122 and Pigment Red 202; (yellow) Pigment
Yellow 14, Pigment Yellow 74, Pigment Yellow 95, Pigment Yellow
110, Pigment Yellow 114, Pigment Yellow 128 and Pigment Yellow 155;
(red) Pigment Orange 5, Pigment Orange 34, Pigment Orange 43,
Pigment Orange 62, Pigment Red 17, Pigment Red 49:2, Pigment Red
112, Pigment Red 149, Pigment Red 177, Pigment Red 178, Pigment Red
188, Pigment Red 255 and Pigment Red 264; (green) Pigment Green 1,
Pigment Green 2, Pigment Green 7 and Pigment Green 36; (blue)
Pigment Blue 60, Pigment Violet 3, Pigment Violet 19, Pigment
Violet 23, Pigment Violet 32, Pigment Violet 36 and Pigment Violet
38; and (black) carbon black. Colorants are referred to herein by
their "C.I" designation established by Society Dyers and
Colourists, Bradford, Yorkshire, UK and published in The Color
Index, Third Edition, 1971. Commercial sources of pigment are
generally well known in the art.
In the case of organic pigments, the ink jet ink may contain up to
approximately 30% pigment by weight, typically about 0.1 to about
25% pigment by weight, and more typically about 0.25 to about 10%
pigment by weight, based on the total ink weight. If an inorganic
pigment is selected, the ink will tend to contain higher weight
percentages of pigment than with comparable inks employing organic
pigment, and may be as high as about 75% in some cases, since
inorganic pigments generally have higher specific gravities than
organic pigments.
Polymeric Dispersant:
The function of the polymeric dispersant is to disperse the solid
particle, more typically a colorant, in the aqueous vehicle. In
accordance with the disclosure, the polymeric dispersant is an AB
block copolymer with crosslinkable functional moieties that are
crosslinked with crosslinking agents selected from the group
consisting of epoxide, carbodiimide, oxazoline, isocyanate, and
silane. These block copolymers may comprise an A block that is
soluble in the ink vehicle components such as glycols and butyl
carbitol, and a B block comprising a random segment of
ionic/potentially ionic and hydrophobic monomers. By `potentially
ionic` it is meant a monomer which may be neutralized to become
ionic such as methacrylic acid (MAA). MAA may be neutralized with
KOH to become an ionic monomer unit. The number of units in the A
block can be about 5 to about 18, more typically about 6 to about
12, still more typically about 8 to about 12, and most typically
about 8 units. The number of units in the B block can be about 15
units to about 80 units, more typically about 25 units to about 70
units and most typically about 30 units to about 50 units.
Typically, the B block provides ionic stabilization whereas the A
block provides steric stabilization in the ink vehicle. These
dispersants provide excellent image properties (O.D. and
durability) while facilitating robust ink formulations and
pragmatic dispersion processes.
Pigments are insoluble particles in the ink vehicle and must be
treated in order to form a stable dispersion. The pigments are
first dispersed in the aqueous vehicle by a block copolymer
dispersant having two blocks (or segments), an A block and a B
block. The A block, is an ink vehicle soluble segment of the
polymer which provides some steric stabilization in the ink vehicle
while also enhancing the surface-activity of the dispersant. The B
block is a random segment comprising ionic/potentially-ionic
monomers and hydrophobic monomers providing pigment anchoring. The
overall polymeric dispersant has a number average molecular weight
(Mn) of about 2,000 to about 20,000 Daltons, more typically about
4,000 to about 12,000 Daltons, and an acid number of about 40 to
about 220 (mg KOH/g polymer solids) more typically about 50 to
about 150 (mg KOH/g polymer solids). The weight ratio of pigment to
dispersion (P/D) is typically between about 0.5 and 5. To further
form a stable dispersion of the pigment with the crosslinked
polymer matrix, a crosslinking compound is then mixed with the
dispersion. The polymeric dispersant with crosslinkable moiety
undergoes a crosslinking reaction and forms a crosslinked network
to entrap the pigment suspended in aqueous vehicle; wherein the
aqueous dispersion has a pH of at least about 8.0.
The print properties of the inks are especially enhanced in the
presence of metal salts, for example calcium carbonate/-chloride
treated papers (ColorLok) and underprinting with salt latent inks
such as magnesium nitrate cyan inks.
A Block Composition:
The function of the A Block is to provide steric stabilization in
the ink vehicle leading to stability of the dispersion in the
presence of organic components which can be in the ink vehicle that
is also known as the aqueous carrier medium. Organic components
often contribute to flocculation of aqueous pigment dispersions.
When the A block of an AB diblock dispersant has good solubility in
the organic components, resistance to flocculation can be markedly
improved through the extension of the A block out from the pigment
surface in the ink vehicle leading to entropic repulsion/steric
stabilization. Furthermore, typical A block monomers can be
non-ionic, hydrophilic and increase surface-activity of the
dispersant.
The constituent monomer(s) of the A block can be hydrophilic or
hydrophobic depending on the properties of the organic components,
and they may include monomers which are constituents of the B
block. Structural similarity between the A block and the organic
components in the ink vehicle will generally result in good
compatibility and steric stabilization.
The A block comprises at least 50% by weight of a monomer, having
the following structure:
CH.sub.2.dbd.CRC(O)O(CHR.sub.1CH.sub.2O).sub.nR.sub.2 wherein R and
R.sub.1 are H, or methyl; R.sub.2 is alkyl of 1-4 carbon atoms or
phenyl; and n is about 1 to about 20, more typically about 1 to
about 10.
Depending on the number, n, of oxyethylene units, the polymers can
be just hydrophilic but water insoluble to completely water
soluble. The solubility of the polymer increases as the number of
oxyethylene units increases. Typical monomers for the A block can
be ethoxy triethylene glycol methacrylate, n-butoxyethyl
methacrylate and mixtures thereof. The A block can also function to
improve polymer properties even in the absence of organic
cosolvents
It has been found that n-butoxyethyl methacrylate has good
compatibility with butyl cellosolve or butyl carbitol, and ethoxy
triethylene glycol methacrylate has good compatibility with glycols
such as ethylene glycol, diethylene glycol, and tripropylene
glycol. In addition, propoxylated methacrylates are soluble in
propylene glycols whereas poly(ethoxy-triethylene
glycol)methacrylate has good compatibility with poly(ethylene
oxide) as well as water.
The A block can also contain other monomers that may or may not
have crosslinkable moieties, that are present in amounts of less
than 50% by weight, and that can be similar to constituents of the
B block. Examples of other monomers that can be incorporated in the
A block include hydroxyethylmethacrylate, methyl methacrylate,
methacrylic acid, butyl methacrylate, and 2-dimethylaminoethyl
methacrylate. These monomers can be advantageously used in the A
block to have crosslinkable functional moieties for further
crosslinking or to adjust the physical properties, e.g., Tg, of the
polymeric dispersant of this disclosure while maintaining the
compatibility with an aqueous dispersion system. However, by the
nature of this disclosure, the A block should have minimal
interaction with the pigment, and thus, strongly anchoring monomer
units, such as styrene, substituted styrene benzyl methacrylate,
phenoxyethyl acrylate, are not desirable.
+B block Composition:
The B block of the AB block copolymer dispersant comprises
ionic/potentially ionic monomers and hydrophobic monomers. The
ratio of the ionic/potentially ionic monomers and hydrophobic
monomer can be about 15 to about 80, more typically about 25 to
about 70, and most typically about 30 to about 50. The
hydrophobicity of the B block in the AB block copolymer dispersants
can be derived from the hydrophobic monomer,
R.sub.3R.sub.4C.dbd.R.sub.5X wherein each of R.sub.3-R.sub.5 are
independently selected from the group consisting of H and an alkyl,
aryl or alkylaryl group having 1-20 carbons, and wherein X is
described below. In one preferred embodiment, each of
R.sub.3-R.sub.5 can be selected from the group consisting of H and
CH.sub.3. In another preferred embodiment, R.sub.3 and R.sub.4 can
be H, and R.sub.5 can independently be selected from H and
CH.sub.3.
In a typical embodiment, X is selected from the group consisting
of: (a) an alkyl, aryl and alkylaryl group containing 1-20 carbon
atoms, which group may further contain one or more heteroatoms such
as O, N, P, S, Si; (b) a group of the formula C(O)OR.sub.6, wherein
R.sub.6 is selected from the group consisting of an alkyl, aryl and
alkylaryl group containing 1-20 carbon atoms, which group may
further contain one or more heteroatoms such as O, N, P, S, Si; and
(c) a group of the formula C(O)NR.sub.7R.sub.8, wherein each of
R.sub.7 and R.sub.8 is independently selected from the group
consisting of H and an alkyl, aryl and alkylaryl group containing
1-20 carbon atoms, which group may further contain one or more
heteroatoms such as O, N, P, S, Si.
Typical hydrophobic monomers in general include, for example,
benzyl methacrylate, butyl methacrylate, methyl methacrylate, ethyl
methacrylate, propyl methacrylate, hexyl methacrylate, 2-ethylhexyl
methacrylate, octyl methacrylate, lauryl ethacrylate, stearyl
methacrylate, phenyl methacrylate, phenoxyethyl methacrylate,
methacrylonitrile, glycidyl methacrylate, p-tolyl methacrylate,
sorbyl methacrylate, methyl acrylate, ethyl acrylate, propyl
acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate,
octyl acrylate, lauryl acrylate, stearyl acrylate, phenyl acrylate,
phenoxyethyl acrylate, acrylonitrile, glycidyl acrylate, p-tolyl
acrylate, sorbyl acrylate, styrene, alpha-methyl styrene,
substituted styrenes, N-alkyl acrylamides, N-alkyl methacrylamides,
vinyl acetate, vinyl butyrate and vinyl benzoate.
The ionic character of the AB block copolymer dispersant is derived
from the ionic monomer, R.sub.9R.sub.10C.dbd.R.sub.11Z wherein each
of R.sub.9-R.sub.11 are independently selected from the group
consisting of H and an alkyl, aryl or alkylaryl group having 1-20
carbons, and wherein Z, ionic or a potentially ionic moiety, is
described below. In one preferred embodiment, each of
R.sub.9-R.sub.11 is selected from the group consisting of H and
CH.sub.3. In another preferred embodiment, R.sub.9 and R.sub.10 is
H, and R.sub.11 is independently selected from H and CH.sub.3.
The Z group can be anionic, cationic, amphoteric or zwitterionic.
Some examples of the Z group include anionic groups selected from
the group consisting of sulfonates, sulfate, sulfosuccinate,
carboxylate, and phosphate; cationic groups such as amine salts,
including quaternary amine salts; amphoteric groups; and
zwitterionic groups selected from the group consisting of betaine,
+N--C--CO2-, and lecithin. The hydrophilic monomers may have single
Z substituents or combinations of Z groups. The Z group is present
as its hydrogen substituted form or as a salt.
Typical ionic monomers include, for example, methacrylic acid,
acrylic acid, maleic acid, maleic acid monoester, itaconic acid,
itaconic acid monoester, crotonic acid, crotonic acid monoester,
N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl
methacrylate, N,N-dimethylaminoethyl acrylate,
N,N-diethylaminoethyl acrylate, t-butylaminoethyl methacrylate,
t-butylaminoethyl acrylate, vinyl pyrridine, N-vinyl pyrridine, and
2-acrylamido-2-propane sulfonic acid.
Examples of polymerization methods include but are not limited to
free radical processes, Group Transfer Processes (GTP), radical
addition fragmentation (RAFT), atom transfer reaction (ATR), and
the like.
The overall polymeric dispersant can have a number average
molecular weight (Mn) of about 2,000 to about 20,000 Daltons, more
typically about 4,000 to about 12,000 Daltons, and an acid number
of about 40 to about 220 (mg KOH/g polymer solids), more typically
of about 50 to about 150. The weight ratio of pigment to dispersion
(P/D) can be typically between about 0.5 and about 5.
The crosslinked polymeric dispersant can be typically present in
the amount of about 0.1 to about 20% by weight, more typically in
the range of about 0.2 to about 10% by weight, and still more
typically in the range of about 0.25% to about 5% by weight, based
on the total weight of the ink jet ink.
Crosslinked Polymeric Dispersant
Furthermore, the polymeric dispersants can have crosslinkable
functional moieties which may be in the A block or B block. The
dispersant is thus capable of crosslinking to a crosslinking
compound that has crosslinking functionality reactive with
crosslinkable moieties. Table 1 identifies suitable functional
groups that may be incorporated into the A block or B block of the
polymeric dispersant and the companion crosslinking groups that may
be present in the crosslinking compound.
TABLE-US-00001 Crosslinkable moieties Crosslinking group Acid
Epoxide, carbodiimide, oxazoline Hydroxyl Epoxide, silane,
isocyanate
As noted above, the functional moieties can be incorporated into
the A block or B block of the polymeric dispersant by selection of
appropriate monomers. Mixtures of these crosslinking moieties may
also be present in the polymeric dispersant. A separate
crosslinking compound having the appropriate group can be added to
the dispersion to crosslink the polymeric dispersant. Useful
crosslinking compounds are those which are soluble or insoluble in
the aqueous vehicle, including m-tetramethylxylene diiscyanate
(TMXDI), isophorone diisocyanate (IPDI), trimethylopropane
polyglycidyl ether, polyglycerol polyglycidyl ether,
oxazoline-functional polymers, waterborne polycarbodiimide resin,
and silane. After the completion of the crosslinking, pH of the
crosslinked dispersion can be adjusted to at least about 8.0, more
typically about 8.0 to 12.0, and most typically about 8.0 to about
11.0.
Preparation of Solid Particle Dispersion and Crosslinking of the
Dispersants
The dispersions of the present disclosure may be prepared using any
conventional milling process known in the art. Most milling
processes use a two-step process involving a first mixing step
followed by a second grinding step. The first step comprises the
mixing of all the ingredients, i.e., particle, dispersant(s),
liquid carrier(s), pH adjuster and any optional additives, to
provide a blended "premix". Typically all liquid ingredients are
added first, followed by the dispersant(s) and lastly the solid
particle. Mixing is generally done in a stirred mixing vessel and
High Speed Dispersers, (HSD), are particularly suitable for the
mixing step. A Cowels type blade attached to the HSD and operated
at 500 rpm to 4000 rpm, and typically 2000 rpm to 3500 rpm,
provides optimal shear to achieve desired mixing. Adequate mixing
is usually achieved by mixing for about 15 minutes to about 120
minutes.
The second step comprises milling of the premix to produce a stable
dispersion. A typical milling process for carbon black pigments
that avoids media contamination is the Microfluidizer Process,
although other milling techniques can be used. In a specific
embodiment, a labscale model M-110Y High Pressure Pneumatic,
Microfluidizer with a diamond Z-Chamber from Microfluidics of
Newton, Mass. can be used. The Microfluidizer uses an impingement
process at high pressures to deaggomerate and mill fine particles,
such as pigments. The model M-110Y Microfluidizer can operate at
pressure ranges of about 3,000 to about 23,000 psi, although
pressures of about 10,000 to about 15,000 are typical. The flow
rates through the microfluidizer were typically about 200 to about
500 ml/min. and more typically about 300 to about 450 ml/min.
The milling can be done using a staged procedure in which a
fraction of the solvent may be held out of the grind and added
after milling is completed. This amount of solvent held out during
milling can vary by dispersion and is typically about 100 to about
300 grams of the total 600 gram batch size. This can be done to
achieve optimal rheology and viscosity for grinding efficiency.
Each dispersion can be processed for a total of 10 passes through
the mill although the endpoint can be achieved in less milling
time.
After completion of milling process, dispersant crosslinking then
takes place by adding the crosslinking compound to the particle
dispersion. To facilitate the crosslinking reaction, it may be
desirable to add a catalyst and/or to elevate the temperature of
the mixture. Useful catalysts can be those that are either soluble
or insoluble in the liquid and can be selected depending upon the
crosslinking reactions. Some suitable catalysts include dibutyltin
dilaurate (DBTDL), tributyl amine ("TBA") and dimethyldodecyl
amine. After completion of the crosslinking, pH of the crosslinked
dispersion can be adjusted to at least about 8.0, more typically
about 8.0 to 12.0, and most typically about 8.0 to about 11.0, if
needed. Then the dispersion can be filled into a polyethylene
container. Optionally, the dispersion can be further processed
using conventional filtration procedures known in the art. The
dispersions can be processed using ultrafiltration techniques to
remove co-solvent(s) and other contaminants, ions or impurities
from the dispersion. Each dispersion can be then tested for pH,
conductivity, viscosity and particle size. Dispersion stability is
deemed important to demonstrating the utility of the dispersing
resins. Dispersion stability testing included measuring pH,
conductivity, viscosity and particle size after oven aging of
samples for 1 week at 70.degree. C. and noting if significant
change versus initial readings had occurred.
Pigmented dispersions can be prepared using the pigment identified
earlier. The premix can be prepared at typically 23% pigment
loading and the dispersant level was set at a P/D
(pigment/dispersant), most typically at a P/D of 2.5. A P/D of 2.5
corresponds to a 40% dispersant level on pigment The dispersant
resins can be neutralized with either alkali metal hydroxide such
as LiOH, KOH, NaOH, or amine to facilitate solubility and
dissolution into water. The neutralization process can be done
either in situ during the premix stage or by pre-neutralizing the
resin during the final stage of manufacture.
During the premix stage the pigment level can be maintained at
about 18% to about 30%, more typically about 23%, and was reduced
to about 12% to about 18%, more typically about 15% during the
milling stage by adding deionized water for optimal milling
conditions. After completing the milling process, the dispersions
can be reduced to about 10% pigment concentration by adding the
de-ionized water and then crosslinked with additional crosslinking
compound by thorough mixing at room temperature or elevated
temperature for several hours. Next, the treated dispersion can be
filtered through a filter, for example, a 0.3 micron Chipwich
filter, available from Pall Trincor of East Falls, N.Y., to remove
any possible contaminants and placed in a 1000 ml polyethylene
container.
Ink Vehicle
The pigmented ink of this disclosure comprises an ink vehicle
typically an aqueous ink vehicle, also known as an aqueous carrier
medium, the aqueous dispersion and optionally other
ingredients.
The ink vehicle is the liquid carrier (or medium) for the aqueous
dispersion(s) and optional additives. The term "aqueous ink
vehicle" refers to an ink vehicle comprised of water or a mixture
of water and one or more organic, water-soluble vehicle components
commonly referred to as co-solvents or humectants. Selection of a
suitable mixture depends on requirements of the specific
application, such as desired surface tension and viscosity, the
selected pigment, drying time of the pigmented ink jet ink, and the
type of paper onto which the ink will be printed. Sometimes in the
art, when a co-solvent can assist in the penetration and drying of
an ink on a printed substrate, it is referred to as a
penetrant.
Examples of water-soluble organic solvents and humectants include:
alcohols, ketones, keto-alcohols, ethers and others, such as
thiodiglycol, sulfolane, 2-pyrrolidone,
1,3-dimethyl-2-imidazolidinone and caprolactam; glycols such as
ethylene glycol, diethylene glycol, triethylene glycol,
tetraethylene glycol, propylene glycol, dipropylene glycol,
tripropylene glycol, trimethylene glycol, butylene glycol and
hexylene glycol; addition polymers of oxyethylene or oxypropylene
such as polyethylene glycol, polypropylene glycol and the like;
triols such as glycerol and 1,2,6-hexanetriol; lower alkyl ethers
of polyhydric alcohols, such as ethylene glycol monomethyl ether,
ethylene glycol monoethyl ether, diethylene glycol monomethyl,
diethylene glycol monoethyl ether; lower dialkyl ethers of
polyhydric alcohols, such as diethylene glycol dimethyl or diethyl
ether; urea and substituted ureas.
A mixture of water and a polyhydric alcohol, such as diethylene
glycol, is typical as the aqueous ink vehicle. In the case of a
mixture of water and diethylene glycol, the ink vehicle usually
contains from about 30% water/about 70% diethylene glycol to about
95% water/about 5% diethylene glycol. The more typical ratios are
about 60% water/about 40% diethylene glycol to about 95%
water/about 5% diethylene glycol. Percentages are based on the
total weight of the ink vehicle. A mixture of water and butyl
carbitol is also an effective ink vehicle.
The amount of ink vehicle in the ink is typically in the range of
about 70% to about 99.8%, and more typically about 80% to about
99.8%, based on total weight of the ink.
The ink vehicle can be made to be fast penetrating (rapid drying)
by including surfactants or penetrating agents such as glycol
ethers and 1,2-alkanediols. Glycol ethers include ethylene glycol
monobutyl ether, diethylene glycol mono-n-propyl ether, ethylene
glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl
ether, ethylene glycol mono-n-butyl ether, ethylene glycol
mono-t-butyl ether, diethylene glycol mono-n-butyl ether,
triethylene glycol mono-n-butyl ether, diethylene glycol
mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol
mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene
glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether,
dipropylene glycol mono-n-butyl ether, dipropylene glycol
mono-n-propyl ether, and dipropylene glycol mono-isopropyl ether.
1,2-Alkanediols are typical. 1,2-C4-6 alkanediols, are more
typical, 1,2-hexanediol, is most typical. Some suitable surfactants
include ethoxylated acetylene diols (e.g. Surfynol.RTM. series from
Air Products), ethoxylated alkyl primary alcohols e.g. Neodol.RTM.
series from Shell) and alkyl secondary alcohols (e.g. Tergitol.RTM.
series from Union Carbide) alcohols, sulfosuccinates (e.g.
Aerosol.RTM. series from Cytec), organosilicones (e.g. Silwet.RTM.
series from Witco) and fluoro surfactants (e.g. Zonyl.RTM. series
from DuPont).
The amount of glycol ether(s) and 1,2-alkanediol(s) added should be
properly determined, but it is typically in the range of from about
1 to about 15% by weight, and more typically about 2 to about 10%
by weight, based on the total weight of the ink. Surfactants may be
used, typically in the amount of about 0.01 to about 5% and
typically about 0.2 to about 2%, based on the total weight of the
ink.
Biocides may be used to inhibit growth of microorganisms.
Pigmented ink jet inks typically have a surface tension in the
range of about 20 mN.m.sup.-1 to about 70 mN.m.sup.-1, at
25.degree. C. Viscosity can be as high as 30 mPas at 25.degree. C.,
but is typically somewhat lower. The ink has physical properties
compatible with a wide range of ejecting conditions, materials
construction and the shape and size of the nozzle. The inks should
have excellent storage stability for long periods so as not clog to
a significant extent in an ink jet apparatus. Further, the ink
should not corrode parts of the ink jet printing device it comes in
contact with, and it should be essentially odorless and
non-toxic.
Although not restricted to any particular viscosity range or
printhead, the inks of the disclosure are particularly suited to
lower viscosity applications. Thus the viscosity (at 25.degree. C.)
of the inks of this disclosure may be less than about 7 mPas, or
less than about 5 mPas, and even, advantageously, less than about
3.5 mPas.
Method of Printing:
A typical printer will generally comprise at least four differently
colored inks such as a cyan, magenta, yellow and black (CMYK) ink.
Ink sets may further comprise one or more "gamut-expanding" inks,
including different colored inks such as an orange ink, a green
ink, a violet ink, a red ink and/or a blue ink, and combinations of
full strength and light strengths inks such as light cyan and light
magenta. In addition, ink sets may include one or more colorless
inks which are printed in combination with the colored inks to
enhance properties such as optical density, chroma, durability
and/or gloss.
According to one embodiment of the disclosure, a method of ink jet
printing onto a substrate is provided comprising, in any workable
order, the steps of: (a) providing an ink jet printer that is
responsive to digital data signals; (b) loading the printer with a
substrate to be printed; (c) loading the printer with an aqueous
ink jet ink comprising an ink vehicle and an aqueous dispersion,
wherein the aqueous dispersion comprises a colorant and a
crosslinked polymeric dispersant, wherein the polymeric dispersant
is a block copolymer comprising an A block and a B block, wherein
the A block is a segment having a block size of about 5 to about 18
units, and comprises at least 50% by weight of a monomer, having
the following structure:
CH.sub.2.dbd.CRC(O)O(CHR.sub.1CH.sub.2O)nR.sub.2 wherein R and
R.sub.1 are H, or methyl; R.sub.2 is alkyl of 1-4 carbon atoms or
phenyl; and n is about 1 about 20; and
the B block is a segment comprising an ionic monomer and at least
one hydrophobic monomer; and wherein the dispersant comprises a
crosslinking moiety; wherein the crosslinking moiety is crosslinked
with a crosslinking agent selected from the group consisting of
epoxide, carbodiimide, oxazoline, isocyanate, and silane; and
wherein the aqueous dispersion has a pH of at least about 8.0; and
(d) printing onto the substrate using the aqueous ink jet ink, in
response to the digital data signals to form a printed image on the
substrate.
The inks of the present disclosure can be printed with any suitable
inkjet printer, including printers equipped with piezo or thermal
print heads. Some examples of thermal ink jet print heads are the
Hewlett Packard Deskjet, and Canon iPIXMA iP4200, and some examples
of piezo print heads are Brother MFC3360C, and Epson Stylus C120.
Some suitable print heads are disclosed in U.S. Pat. No. 6,161,918,
U.S. Pat. No. 4,490,728, and U.S. Pat. No. 6,648,463, the
disclosures of which are incorporated herein by reference. The
substrate can be any suitable substrate including plain paper, such
as common electrophotographic copier paper; treated paper, such as
photo-quality inkjet paper. The present disclosure is particularly
advantageous for printing on plain paper.
The following examples illustrate the disclosure without, however,
being limited thereto.
EXAMPLES
In the following examples, unless otherwise stated, water was
deionized and ingredient amounts were in weight percent of the
total weight of ink.
Glossary:
Crosslinking Compounds from Nagase Chemicals Ltd. (Osaka,
Japan):
Denacol.RTM. 321: Trimethylolpropane Polyglycidyl Ether
Denacol.RTM. 920: Polypropylene Glycol Diglycidyl Ether,
Denacol.RTM. 512: Polyglycerol Polyglycidyl Ether
Polymeric Dispersants:
The dispersant polymers used to make the dispersions were
synthesized by established methods as described, for example, in
U.S. Pat. Nos. 5,085,698. and 5,852,075 along with U.S. patent
publication US200510090599, the disclosures of which are
incorporated by reference herein as if fully set forth.
It should be noted that, in referring to the polymer compositions,
a double slash indicates a separation between blocks and a single
slash indicates a random copolymer. Thus, BzMA//MAA//BzMA 8//10//8
is an ABA triblock polymer with a first A block that is on average
8 BzMA (Benzyl Methacrylate) units long, a B block that is on
average 10 MAA (Methacrylic Acid) units long, and a final A block
that is on average 8 BZMA units long.
The following synthetic examples were all based on group transfer
polymerization (GTP), although other types of polymerization
processes can be used to generate similar types of polymers. In the
case of the block polymers, the current block was at least 95%
converted before adding the mixture of monomers for the next block.
In all cases, the feed cycle strategy is described. However, the
synthesis was terminated when 99% of the monomer was converted as
detected by HPLC with mesitylene as an internal standard. The
molecular weight reported (unless otherwise noted) was based on
theoretical considerations. For the random linear polymers, all
monomer ratios were reported as the mole ratios of the monomer
components, and represented the theoretical degree of
polymerization for each block or set of monomer units. Polymeric
dispersants were routinely synthesized in dry THF and converted to
a solution in 2-pyrrolidone (2P) by distilling the THF while
replacing with 2P.
Standard laboratory techniques for handling water sensitive
chemicals were employed for the following examples. For example,
glassware was extensively dried before use, monomers were stored
over sieves, and cannulation procedures were used to keep material
dry.
Gel Permeation Chromatography or GPC was used to verify predicted
molecular weight and molecular weight distribution. The GPC system
included a Waters 1515 Isocratic HPLC Pump, Waters 2414 Refractive
Index Detector, 717 plus Waters Autosampler, Four Styregel Columns
(HR 0.5, HR 1, HR 2, and HR 4) in series in a Waters Column Heater
set to 40.degree. C. Samples were eluted with Tetrahydrofuran (THF)
at a flow rate of 1 mL/min. The samples were analyzed using Breeze
3.30 Software with a calibration curve developed from narrow
molecular weight, polymethylmethacrylate (PMMA) standards. Based on
light scattering data from Polymer Laboratories Ltd., the nominal,
peak molecular weight for the PMMA standards were as follows:
300000, 150000, 60000, 30000, 13000, 6000, 2000, and 1000.
The particle size was determined by dynamic light scattering using
a Microtrac Analyzer, Largo Fla. For many of the dispersion steps,
a Model 100 F or Y, Microfluidics System was used (Newton
Mass.).
The polymeric dispersants are summarized in the table below.
Details include dispersant # from cross-referencing with ink and
pigment dispersion data, polymer structure in terms of DP or chain
length for each monomer unit, architecture (diblock vs random),
theoretical number average molecular weight (Mn), and theoretical
acid number (mg KOH/g solids). The measured acid number and Mn by
GPC are included in the polymer preparation. Note, the polymer
composition may also be expressed in terms of weight % for each
monomer component. However, in an effort to facilitate comparison
between random and block copolymer, these polymer structure are
represented in the detailed fashion of monomer unit DP.
TABLE-US-00002 TABLE 1 Polymer Theor. Dispersant # Structure (DP)
Architecture Theor. Mn Acid # Dispersant 1 8ETEGMA// Diblock 7720
81 30BzMA/11MAA Dispersant 2 8ETEGMA// Diblock 7260 93 30BMA/11MAA
Dispersant 3 8ETEGMA// Diblock 11838 95 49BzMA/20MAA Comp
22BzMA/11MAA Random 4818 137 Dispersant 1 Comp 13BzMA//10MAA
Diblock 3148 190 Dispersant 2
Dispersant 1: Diblock 8ETEGMA//30BzMA/11MAA
A 5-liter round bottom flask was dried with a heat gun under
nitrogen purge and equipped with a mechanical stirrer,
thermocouple, N.sub.2 inlet, drying tube outlet, and addition
funnels. Tetrahydrofuran (THF), 2777 g, was cannulated to the
flask. Initiator (1,1-bis(trimethylsilyloxy)-2-methyl propene,
120.9 g (0.521 moles)) was injected followed by catalyst
(tetrabutyl ammonium m-chlorobenzoate, 3.13 ml of a 1.0 M solution
in acetonitrile). Catalyst solution (tetrabutyl ammonium
m-chlorobenzoate, 2.4 ml of a 1.0 M solution in acetonitrile and
THF, 10.9 g) was syringe pumped during both the monomer feeds.
Monomer feed 1 (trimethylsilyl methacrylate 906 g (5.73 mol) and
Benzyl methacrylate, 2752.3 g (15.63 mol)) was added over 60
minutes while the reaction exo-thermed to 65.degree. C. After a 1
hr hold, HPLC indicated greater than 95% monomer conversion, and
then, monomer feed II (ethyl triethylene glycol methacrylate,
1027.1 g (4.17 mol)) was added over 15 minutes.
The ETEGMA conversion was greater than 98% 90 min after the feed
was complete. 400.34 g of methanol were added, and then the THF and
other volatile by-products were distillated by slowly heating to
120.degree. C. while adding 2-pyrrolidone (2P). The final polymer
solution was 45.1% solids with a measured number of 85.2 mg
KOH/gram of polymer solids. The molecular weight of this polymer as
measured by GPC was Mn 8543, Mw 9568, and PD 1.12.
Dispersant 2: Diblock 8ETEGMA//30BMA/11MAA
A 5-liter round bottom flask was dried with a heat gun under
nitrogen purge and equipped with a mechanical stirrer,
thermocouple, N.sub.2 inlet, drying tube outlet, and addition
funnels. Tetrahydrofuran (THF), 2423 g, was cannulated to the
flask. Initiator (1,1-bis(trimethylsilyloxy)-2-methyl propene,
98.82 g (0.426 moles)) was injected followed by catalyst
(tetrabutyl ammonium m-chlorobenzoate, 2.6 ml of a 1.0 M solution
in acetonitrile). Catalyst solution (tetrabutyl ammonium
m-chlorobenzoate, 2.1 ml of a 1.0 M solution in acetonitrile and
THF, 16.1 g) was syringe pumped during both the monomer feeds.
Monomer feed 1 (trimethylsilyl methacrylate 728.7 g (4.61 mol) and
butyl methacrylate, 1790.9 g (12.61 mol)) was added over 60 minutes
while the reaction exo-thermed to 65.degree. C. After a 1 hr hold,
HPLC indicated greater than 95% monomer conversion, and then,
monomer feed II (ethyl triethylene glycol methacrylate, 825.3 g
(3.35 mol)) was added over 15 minutes.
The ETEGMA conversion was greater than 98% 90 min after the feed
was complete. 322.6 g of methanol were added, and then the THF and
other volatile by-products were distillated by slowly heating to
120.degree. C. while adding 2-pyrrolidone (2P). The final polymer
solution was 45.1% solids with a measured number of 98.2 mg
KOH/gram of polymer solids. The molecular weight of this polymer as
measured by GPC was Mn 9018, Mw 9635, and PD 1.07.
Dispersant 3: Diblock 8ETEGMA//49BzMA/20MAA
A 5-liter round bottom flask was dried with a heat gun under
nitrogen purge and equipped with a mechanical stirrer,
thermocouple, N.sub.2 inlet, drying tube outlet, and addition
funnels. Tetrahydrofuran (THF), 1046 g, was cannulated to the
flask. Initiator (1,1-bis(trimethylsilyloxy)-2-methyl propene, 34.7
g (0.150 moles)) was injected followed by catalyst (tetrabutyl
ammonium m-chlorobenzoate, 0.9 ml of a 1.0 M solution in
acetonitrile). Catalyst solution (tetrabutyl ammonium
m-chlorobenzoate, 0.7 ml of a 1.0 M solution in acetonitrile and
THF, 3 g) was syringe pumped during both the monomer feeds. Monomer
feed 1 (trimethylsilyl methacrylate 459.5 g (2.91 mol) and benzyl
methacrylate, 1253.2 g (7.12 mol)) was added over 60 minutes while
the reaction exo-thermed to 65.degree. C. After a 1 hr hold, HPLC
indicated greater than 95% monomer conversion, and then, monomer
feed II (ethyl triethylene glycol methacrylate, 286 g (1.16 mol))
was added over 20 minutes.
After 1 hr relux, the ETEGMA conversion was greater than 97%. Then,
195 g of methanol were added, and THF and other volatile
by-products were distillated by slowly heating to 120.degree. C.
while adding 2-pyrrolidone (2P). The final polymer solution was
41.3% solids with a measured number of 95.6 mg KOH/gram of polymer
solids.
Comparative Dispersant 1: Random 22BzMA/11MAA
A 5-liter round bottom flask was dried with a heat gun under
nitrogen purge and equipped with a mechanical stirrer,
thermocouple, N.sub.2 inlet, drying tube outlet, and addition
funnels. Tetrahydrofuran (THF), 902 g, was cannulated to the flask.
Initiator (1,1-bis(trimethylsilyloxy)-2-methyl propene, 55 g (0.233
moles)) was injected followed by catalyst (tetrabutyl ammonium
m-chlorobenzoate, 0.6 ml of a 1.0 M solution in acetonitrile).
Catalyst solution (tetrabutyl ammonium m-chlorobenzoate, 0.6 ml of
a 1.0 M solution in acetonitrile and THF, 29.0 g) was syringe
pumped during both the monomer feeds. Monomer feed 1
(trimethylsilyl methacrylate 412 g (2.59 mol) and Benzyl
methacrylate, 918 g (6.46 mol)) was added over 45 minutes while the
reaction exo-thermed to 65.degree. C. After a 1 hr hold, HPLC
indicated greater than 98% monomer conversion, then 182.07 g of
methanol were added. Then, the THF and other volatile by-products
were distillated by slowly heating to 120.degree. C. while adding
2-pyrrolidone (2P). The final polymer solution was 45.54% solids
with a measured number of 132.7 mg KOH/gram of polymer solids.
Comparative Dispersant 2: Diblock 13BzMA//10MAA
A 5-liter round bottom flask was dried with a heat gun under
nitrogen purge and equipped with a mechanical stirrer,
thermocouple, N.sub.2 inlet, drying tube outlet, and addition
funnels. Tetrahydrofuran (THF), 802 g, was cannulated to the flask.
Initiator (1,1-bis(trimethylsilyloxy)-2-methyl propene, 81.5 g
(0.345 moles)) was injected followed by catalyst (tetrabutyl
ammonium m-chlorobenzoate, 0.85 ml of a 1.0 M solution in
acetonitrile). Catalyst solution (tetrabutyl ammonium
m-chlorobenzoate, 0.85 ml of a 1.0 M solution in acetonitrile and
THF, 7.35 g) was syringe pumped during the monomer feed. Monomer
feed (trimethylsilyl methacrylate 554.9 g (3.53 mol), was added
over 45 minutes while the reaction exo-thermed to 72.degree. C.
After a 1 hr hold, HPLC indicated greater than 97% monomer
conversion, and then, monomer feed II Benzyl Methacrylate 803.5 g
(5.10 mol), was added over 45 minutes. After a 60 min hold, HPLC
indicated greater than 99% monomer conversion.
Then, 247.2 g of methanol were added, and THF and other volatile
by-products were distillated by slowly heating to 120.degree. C.
while adding 2-pyrrolidone (2P). The final polymer solution was
40.55% solids with a measured number of 190.4 mg KOH/gram of
polymer solids. The molecular weight of this polymer as measured by
GPC was Mn 4638, Mw 5065, and PD 1.09.
Preparation of Pigmented Dispersions
The carbon black pigmented dispersions were prepared using
Degussa's Nipex.RTM. 180 IQ carbon black pigment. Each carbon black
premix was prepared at 23% pigment loading and the amount of
dispersant was set at a P/D (pigment/dispersant) of 2.0 that
corresponded to a 50% level of active dispersant on pigment.
Neutralization of the dispersants was done using a 45.6% active KOH
solution. The neutralization process was done "In Situ" in the
Premix step for Pigment Dispersions 1.
Pigment Dispersion 1:
Pigment Dispersion1 was prepared using a two step process in which
the dispersion ingredients were added to a 1 Liter stainless steel
pot in the order shown below. The premix step used a High Shear
Disperser, HSD, with a 60 mm Cowels blade operated at 3500 rpm
which ran for 2 hours. The pigment dispersion milling was performed
using a labscale model M-110Y High Pressure Pneumatic,
Microfluidizer with a diamond Z-Chamber available from
Microfluidics, a division of Microfluidics International
Corporation, Newton, Mass. Pigment Dispersion 1 was processed at a
pressure of 15,000 psi for a total of 12 passes through the
Microfluidizer.
Step 1: Premix
A 2200 gram dispersion sample was prepared by adding the following
ingredients, in the order listed below, to a 1 Liter stainless
steel pot. Each ingredient was added slowly with mixing using an
HSD, High Shear Disperser, equipped with a 60 mm Cowels blade and
operated at roughly 1000 rpm during ingredient loading. The pigment
loading in the premix step was 23%.
TABLE-US-00003 Ingredients Amount (g) Deionized water 741.05
Dispersant 1 (BzMA/MAA//ETEGMA 30/11//8) 340.56 KOH Solution (45.6%
Active) 23.2 Nipex .RTM. 180 carbon black pigment 330.
After all ingredients were loaded, the High Speed Disperser speed
was increased to 3500 rpm and the contents were processed for 2
hours. Next, additional deionized water (765 grams) was added to
reduce the pigment level in the dispersion to 15% which is the
level used in the Microfludization milling stage.
Step 2: Milling
The premix prepared in Step 1 was milled using a labscale model
M-110Y High Pressure Pneumatic, Microfluidizer, with a diamond
Z-Chamber from Microfluidics, Newton, Mass. The dispersion was
milled for a total of 12 passes at a flow-rate of 440 ml/min and
pressure of 15,000 psi. After milling was completed at 15% pigment,
the dispersion was filtered through a 0.3 micron Chipwich filter
available from Pall Trincor, East Falls, N.Y. and collected into a
3000 ml polyethylene container. The final pigment dispersion batch
size totaled 2200 grams. The properties of pH, viscosity, particle
size (D50 and D95 in nm) and Accusizer of the pigment dispersion
were tested and are reported in Table 2.
Pigment Dispersion 2 (Magenta):
Pigment Dispersion 2 was made using a media milling process and a
lab-scale Eiger Minimill, model M250, VSE EXP from Eiger Machinery
Inc. Chicago, Ill. The first step comprised the mixing of all the
ingredients, that is, pigment, dispersants, KOH, pH adjuster, to
provide a blended "premix". All liquid ingredients were added
first, followed by the KOH solution which was used to neutralize
"in situ" the dispersant and lastly the pigment. Mixing was done in
a stirred 10 Liter stainless steel mixing vessel using a high-speed
disperser, (HSD), with a 60 mm Cowels type blade attached to the
HSD operated at 3500 rpm for a total mixing time of 2 hrs.
The pigment loading in the premix step was 25%.
TABLE-US-00004 Ingredients Amount (g) Deionized water 460.49
Dispersant 2 (BMA/MAA//ETEGMA 30/11//8) 936.50 KOH Solution (45.6%
Active) 56.90 Pigment Red 122 (Sun chemical) 1610.00
After premixing for 2 hrs. at 3500 rpm using the HSD, additional DI
water was added to reduce pigment loading to 23% which gave the
desired rheology and was the level used during the media milling
stage.
TABLE-US-00005 Ingredients Amount (g) Deionized water 672.2
Next the media milling or grinding step was performed by charging
820 grams of 0.5 YTZ zirconia media to the mill. The dispersion was
processed using a re-circulation grinding process with a mill disk
speed of 3500 rpm and flow rate of 350 grams per min. The milling
was done using a staged procedure in which 20% of the DI water was
held out during the grind and added after milling was completed.
The dispersion was processed for a total of 4 hours milling
time.
After completion of the milling step the final letdown of DI water
was added and mixed in reducing the pigment loading in the
dispersion to 10%.
TABLE-US-00006 Ingredients Amount (g) Deionized water (final
letdown) 1319.3
The pigment dispersion was filtered through a 0.3 micron Chipwich
filter available from Pall Trincor of East Falls, N.Y. and
collected into a 1000 ml polyethylene container. The final pigment
dispersion batch size totaled 5366 grams at 13% pigment
loading.
Pigment Dispersion Comparative Compostions 1 and 2 (Magenta):
Pigment Dispersion Comparative Compositions 1 and 2 were prepared
by a process similar to the Eiger Minimill process described for
Pigment Dispersion 2 with the following exception: Pigment
Dispersion Comparative Composition 1 was Pigment Red 122 dispersed
with Comparative Dispersant 1 (22/11 BzMA/MAA) at a P/D of 2.
Pigment Dispersion Comparative Composition 2 was Pigment Red 122
dispersed with Comparative Dispersant 2 (13//10 BzMA//MAA).
Pigment Dispersion 3 (Yellow):
Pigment Dispersion 3 was prepared by a process similar to the Eiger
Minimill process described for Pigment Dispersion 2 with the
following exception: Pigment Yellow 74 (Sun Chemical) was dispersed
with Dispersant 2 (8ETEGMA//30BMA/11MAA) at a P/D of 2.0.
Pigment Dispersion 4 (Yellow):
Pigment Dispersion 4 was prepared by a process similar to the Eiger
Minimill process described for Pigment Dispersion 2 with the
following exception: Pigment Yellow 74 (Sun Chemical)) was
dispersed with Dispersant 3 (8ETEGMA//49BzMA/20MAA) at a P/D of
2.5.
TABLE-US-00007 TABLE 2 Initial Pigment Dispersion Properties at
Room Temperature Dispersion Accusizer no. Dispersant Pigment pH D50
D95 (.times.10.sup.7 counts/ml) 1 Dispersant 1 Nipex .RTM. 8.54 104
183 16 8ETEGMA//30BzMA/11MAA 180 2 Dispersant 2 PR122 8.08 111 180
6 8ETEGMA//30BMA/11MAA 3 Dispersant 2 Y74 8.03 116 193 7
8ETEGMA//30BMA/11MAA 4 Dispersant 3 Y74 8.10 111 254 200
8ETEGMA//49BzMA/20MAA Comp1 Comp dispersant 1 PR122 8.24 96 165 23
22BzMA/11MAA Comp2 Comp dispersant 2 PR122 7.3 96 168 3
13BzMA//10MAA
Crosslinked Pigment Dispersion Preparation:
In the crosslinking step, crosslinking compound was mixed with the
above pigment dispersion, and heated at 60.degree.-80.degree. C.,
with efficient stirring, for 6 to 8 hours. After crosslinking
reaction was finished, pH was adjusted to at least about 8.0 if
needed. Table 3 summarized the crosslinking recipe for the pigment
dispersion crosslinking. Table 4 summarized the final crosslinked
pigment dispersions physical properties. Since all crosslinked
dispersions had pH above 8.0, no pH adjustment step was performed.
As shown in Table 4, crosslinking had no negative impact on
dispersion particle size and bigs.
TABLE-US-00008 TABLE 3 Crosslinked Dispersion Dispersion
Crosslinking Crosslinking Mole ratio no. no. Pigment moiety
Compound Crosslinker:COOH XL-1A 1 Nipex .RTM. 180 COOH Denacol 321
1:4 XL-1B 1 Nipex .RTM. 180 COOH Denacol 512 1:4 XL-2 2 PR122 COOH
Denacol 321 2:5 XL-3 3 Y74 COOH Denacol 920 1:4 XL-4 4 Y74 COOH
Denacol 321 1:4 XL-Comp1 Comp1 PR122 COOH Denacol 321 1:4 XL-Comp2
Comp2 PR122 COOH Denacol 321 1:4
TABLE-US-00009 TABLE 4 Crosslinked Dispersion Accusizer no. pH D50
D95 (.times.10.sup.7 counts XL-1A 8.66 99 151 16 XL-1B 8.49 102 182
14 XL-2 9.19 103 172 8 XL-3 9.77 101 216 8 XL-4 8.42 121 220 NA
XL-Comp1 8.85 91 177 7 XL-Comp2 8.09 103 170 10
Ink Preparation and Stability Testing:
Inks were prepared by stirring together the pigment dispersion and
the vehicle ingredients listed in Table 5. The dispersion was added
in an amount that provided 3% pigment solids in the final ink. Ink
physical properties including viscosity, pH, particle size (D50) at
room temperature were measured. To test ink stability, above
physical properties were re-measured after heat aged at 60.degree.
C. for 7 days. Pigment particle size growth after dispersion was
formulated into the ink and particle size growth after heated aging
were indications of dispersion instability. Large increase of
viscosity after heat aging was also the indication of dispersion
instability. Stability of pigment dispersions before and after the
crosslinking step was tested. Results were summarized in Table
6.
TABLE-US-00010 TABLE 5 Vehicle Ingredient Butyl Cellosolve 10.0%
Butyl Carbitol 16.0% 2-Pyrrolidone 5.0% Water Balance
TABLE-US-00011 TABLE 6 Ink Stability Results Room Temperature
Viscosity After 7-day at 60.degree. C. % Viscosity % D50 Dispersion
no. pH (cps) D50 (nm) pH Viscosity D50 (nm) change increas 1 8.36
3.78 99.6 7.81 4.17 133.9 10.32% 34% XL-1A 8.22 3.73 103.6 8.02
3.73 111 0.00% 7% XL-1B 8.13 3.79 104.2 7.98 3.73 110.2 -1.58% 6% 2
7.68 gel 97 7.76 gel 474 NA 389% XL-2 8.85 5.3 99.3 8.57 6.03 121.1
13.77% 22% 3 7.98 3.94 89.5 7.80 4.41 243 11.93% 172% XL-3 8.96
5.26 129.5 8.62 5.01 144.5 -4.75% 12% 4 7.29 3.09 100 7.16 4.82
1107 55.99% 1007% XL-4 7.51 3.29 96 7.36 2.85 129 -13.37% 34% Comp1
8.09 8.05 466.0 8.63 4.45 555.0 -44.72% 19% XL-comp1 NA NA 89 NA NA
232 NA 161% Comp2 7.31 34.2 264.8 7.4 gel 272 NA 3% XL-comp2 7.67
6.68 141.8 7.75 8.53 297.4 27.69% 110%
As shown in Table 6, crosslinked dispersions of this disclosure
XL-1A, XL-1B, XL-2, XL-3, and XL-4 all demonstrated improved ink
stability compared to non-crosslinked counterparts. For both
comparative dispersions dispersed with non-inventive dispersants,
crosslinked and noncrosslinked dispersions showed instability.
Crosslinking of the comparative dispersions did not improve
stability. In the case of comp1 and comp2 dispersions, although
increases of particle size after heat aging were small, ink
particle sizes at room temperature were already quite big when inks
were initially made, an indication of instability.
* * * * *